The present invention relates to a photosensitive drum used for forming on its surface an electrostatic latent image for formation of an image in an electrostatic recording process employed in an electrophotographic apparatus or electrostatic recording apparatus, for example, a copying machine, facsimile machine or printer.
An electrostatic recording process employed in a copying machine, facsimile machine or printer adopts the following printing procedure. First, an electrostatic latent image is formed on the surface of a photosensitive drum by uniformly electrifying the surface of the photosensitive drum and projecting an image from an optical system to the surface of the photosensitive drum to erase the electrification of a portion on which light has impinged. Then, toner is supplied to the electrostatic latent image to form a toner image by electrostatic adhesion of the toner, and the resultant toner image is transferred on a recording medium such as a piece of ordinary paper, OHP, or photographic paper.
A related art photosensitive drum used for such an electrostatic recording process generally has a structure shown in FIG. 3.
Referring to FIG. 3, there is shown the related art photosensitive drum including a cylindrical base body 1 made from a metal such as aluminum or a conductive resin, to both ends of which are fixedly fitted flanges 2a and 2b made from a metal or resin. In addition, on the outer peripheral surface of the cylindrical base body 1 is formed a photosensitive layer 3. In general, as shown in FIG. 3, the photosensitive drum is rotatably supported by inserting supporting shafts 4, provided on a main body a of an electrostatic recording apparatus, into shaft holes 5 provided in both the flanges 2a and 2b, respectively; and the drum is rotated by meshing a gear 7, connected to a drive source such as a motor, with a drum driving gear 6 formed around one flange 2b.
The photosensitive drum must be grounded to electrify the photoconductive layer 3 of the photosensitive drum and form an electrostatic latent image on the photoconductive layer 3 by exposure. The related art photosensitive drum, if it has the flanges 2a and 2b made from an insulating resin, is earthed to the apparatus main body a via an earthing metal plate provided on the inner surface side of one of the flanges for bringing the cylindrical base body 1 into conduction with the corresponding one of the supporting shafts 5.
The above-described related art photosensitive drum, however, has problems. Since the photosensitive drum is assembled by fixedly fitting the flanges 2a and 2b to both ends of the cylindrical base body 1, the flange assembling work must be repeated twice for assembling the flanges 2a and 2b to both ends of the cylindrical base body 1. Also since the cylindrical base body 1 and the flanges 2a and 2b are formed separately from each other, each of these parts must be formed with high processing accuracy, thereby increasing the manufacturing cost of the photosensitive drum.
In the case of the related art photosensitive drum requiring the above earthing metal plate, a work of mounting the earthing metal plate must be additionally performed, to thereby further increase the manufacturing cost; and also good conduction between the metal plate and the supporting shaft 5 is possibly lost due to wear of the metal plate during operation of the photosensitive drum, with a result that it is difficult to ensure sufficient reliability of the drum for a long period of time.